INVESTIGATION OF ORDERING KINETICS IN CN(3)AU WITH THE TOMOGRAPHIC ATOM-PROBE

Kinetics of congruent ordering in Cu3Au at 350 degrees C was investiga ted by means of a three-dimensional atom probe. This instrument, calle d a Tomographic Atom Probe (TAP), enables atomic resolution images of a small volume (10 X 10 X 100 nm(3)) of the material reconstructed in the three dimensions of space. The time evolution of ordered domains a t 350 degrees C shows that a t(1/2) law is followed as soon as 5 min. For this aging time, the nucleus diameter is close to 1.7 nm, This sca ling law was observed even before domains came into contact (t = 50 mi n). Competitive growth was observed to start as soon as 5 min. The num ber density was observed to decrease rapidly up to t = 50 min. A slowe r decrease was observed when domains begin to impinge, Experimental co nditions and requirements as well as advantages of TAP as compared to HREM for the study of ordering are discussed in detail.